Ascaris are round worm parasites that live in the intestines of their hosts and are continuously challenged by host pancreatic enzymes. Examination of the contents of Ascaris gut showed that the quantity of inhibitors and of proteases detected will not inactivate the amount of host chymotrypsin that disappears when live worms are challenged with a solution of chymotrypsin under controlled conditions. To determine the fate of host enzymes, fluorescent labeled, fully active, host chymotrypsin will be used to challenge the worms. At various times the worms will be fixed, sectioned and examined for fluorescence that may appear inside. Will such fluorescence be due to the presence of an inactive complex between host enzyme and Ascaris inhibitor? To examine this possibility, the binding of purified antibodies to chymotrypsin and to Ascaris chymotrypsin and to Ascaris chymotrypsin inhibitor will be examined on slices of Ascaris. If the sites of antibody binding and of fluorescence coincide, we may conclude that the host enzymes enter into the parasite as a complex and from their location infer possible uses of host proteins and functions of parasite inhibitors. Ascaris larvae will be isolated from the lungs of hogs. Attempts will be made to complete their development to adults in tissue culture media supplemented with host stomach and intestinal juices. Characterization of trypsin inhibitor from human Ascaris will be completed the sequence of the trypsin inhibitor begun. Chymotrypsin/elastase inhibitor will be isolated from human Ascaris. The sequence of chymotrypsin/elastase inhibitor I from hog Ascaris will be completed. Conditions for the purification of pepsin inhibitor from Ascaris extracts using affinity chromatography will be determined.